1. Field of the Invention
This disclosure relates to the field of electronic cables. In particular, to high speed data cables (category or premise cables) and other cables that utilize fillers or splines.
2. Description of Related Art
Electronic devices, and computers in particular, are starting to become ever more connected. Just 20 years ago the idea of a computer network where machines talked with each other was simply a dream. Streaming media, more intense graphics, and interactive web-based systems are increasingly demanding of speed in network transfer. Today, people from around the world are connected to computer networks which are both local (such as LANs) and worldwide in scope (such as the Internet).
As computers have become increasingly interconnected, there has arisen a more pronounced need for the cables and connectors used to connect them to be able to transfer more information in the same amount of time. While wireless networks have attracted a lot of attention recently, the vast majority of networks, and particularly of high speed networks, still communicate by sending electrical signals across conductors wired between them and therefore, as the networks push to be faster, the cables need to adapt to allow faster communication.
One particularly useful type of cable in the computer networking arena are the so-called “category” cables of which category 6 (or CAT6) is currently one of the standards utilized with category 5 or 5e (CAT5, CAT5e) also being used on a fairly regular basis. In category cable, it is necessary to meet certain performance characteristics set by a standards setting organization (such as the TIA, ISO, or IEEE) for critical performance attributes such as near-end cross-talk (NEXT), cross-talk ratio (ACR), Equal Level Far End Crosstalk (ELFEXT), and the like. Generally, the higher the number of the cable, the more rigorous the requirements and the faster communication the cable is designed for. These standards are set so that networks utilizing the cable can operate and transfer at particular speeds without suffering from loss of data or other problematic concerns. In many respects, the standard defines the label. A CAT6 cable meets certain performance characteristics and therefore can be called “CAT6.” That cable can then also be utilized in a network requiring the specific speed of the standard.
The exacting standards required for data speed and electrical characteristics of CAT6 or higher cable relate in many cases to cross-talk in the cable. This includes NEXT and special categories such as far-end cross-talk (FEXT), and Power Sum NEXT (PSNEXT). Cross-talk is the interference in one channel from an adjacent channel and, in particular, relates to the cross-talk or signal interference between two component cables or wire pairs. Category cables generally utilize four component cables each of which is formed of a twisted pair. Each twisted pair comprises two individual conductors or wires (generally insulated from each other) which are twisted about each other to form a generally double helix shape. Over a length of the component cable, the shape of the twisted pair approaches a cylindrical shape.
Each of these component cables, and any other components included in the cable, are then generally encased in a jacket which forms the resultant cable. Cross-talk occurs when electrical impulses from one component cable (wire pair) can migrate to a different wire pair within this cable. That is, the component cables “talk” in a manner that is undesirable by sharing signals or allowing signals to finish propagating in a component other than the one in which they began propagating. Cross-talk can serve to corrupt data, and in high-speed networks, can cause the network to slow. Cross-talk is a significant concern in trying to build category cable because digital data which is propagated incorrectly can be misunderstood when received and therefore has to be re-sent and/or ignored. The problem is particularly acute in CAT6 cables where, in its optimal format, all four twisted pairs (component cables) are utilized for data transmission.
In many early cable designs, the insulation on each wire in the twisted pair was sufficient to prevent cross-talk between the component cables. Higher standards are generally too rigorous, however, for this limited prevention and it is desirable to further insulate the twisted pairs from each other. This insulation may be performed by physical separation. In most cases, however, the separation cannot be maintained within the resultant cable without additional structure and a physical barrier is necessary.
Previously, twisted pair data cables (category cables) have tried to meet the requirements by using “X”, “+”, or other cross-shaped fillers (or splines as they are sometimes called) which are placed within the cable jacket to separate the twisted pairs from each other. These designs all have the same general layout. There are four twisted-pairs included in the cable which are arranged about the central filler. Each twisted pair is placed in a single “V” formed by two-legs of the cross, placing the material of the filler between each twisted pair. In effect, the two neighboring twisted pairs are separated by a leg of the filler. The filler material (which is generally insulative) then serves to inhibit cross-talk between the different twisted pairs One such cross-shaped filler is described in U.S. Pat. No. 6,297,454, the entire disclosure of which is herein incorporated by reference.
While these fillers have helped improve cross-talk characteristics, they are not necessarily ideal in all situations. Cross-shaped fillers keep the twisted pairs separated by some of the filler material, even when compressed, but often do so at the expense of over-correction. A cross-shaped filler inhibits motion of the component cables and the cross talk between them by placing a physical barrier between each of the component cables. This barrier prevents cross-talk by keeping each pair of component cables separated by the barrier of the material of the spline. However, this physical barrier can be unnecessary with regards to certain of the pairs for the prevention of certain levels of cross talk.
The inclusion of unnecessary material to form the cross-shaped spline for cables designed to meet these standards therefore can make the cross-shaped construction both more expensive and more difficult to manufacture without it being really necessary. Further, because of the excess material within the cable, the resulting cable can have an increased fire risk and is generally more rigid and physically larger in construction than may be necessary. These characteristics can make the cable less useful and harder to work with.
It is therefore desired in the art to have a spline which can provide for inhibition to cross talk between component cables so as to produce cables suitable for meeting certain data transfer requirements, without having to have the expense or manufacturing difficulty of a filler that places unnecessary physical barrier between adjoining component cables when such physical barrier is unnecessary to inhibit the cross talk sufficiently to meet the standard. Alternatively, the removed material can be repositioned in the spline to enhance overall performance at the same general cost.